A study on air-sea exchange processes and conserved variable analysis over the Indian Ocean with INDOEX IFP-99 data

Abstract

The exchange properties across the Marine Boundary Layer influence atmospheric convection and determine to a large extent the atmospheric circulation in the tropics. In view of these phenomena, an analysis of the surface parameters such as sea-surface temperature, air temperature, wind speed, moisture and cloud cover along the ORV Sagar Kanya and Ronald H. Brown cruise track was carried out. An attempt was made to examine the changes in these parameters while the ship was passing across the ITCZ region. The humidity was found to be considerably high over the ITCZ than non-ITCZ regions. The air-sea interaction processes were studied by computing the radiation fluxes (short-wave and longwave) and the turbulent heat fluxes (sensible heat and latent heat) using semi-empirical models. Over ITCZ region a net heat loss was found which can be attributed to large convergence, strong convective activity and dense cloud cover, leading to drastic reduction in short-wave radiation. Latitudinal and longitudinal variation of surface meteorological parameters and turbulent fluxes were studied to establish a link with the prevailing convective and clear weather regimes along the cruise tracks. A conserved variable analysis of the conserved variable such as potential temperature, virtual potential temperature, saturation equivalent potential temperature and specific humidity is carried out at every point of upper air observation from Ronald H. Brown. The values are estimated up to a maximum of 3 km to cover the boundary layer. In the ITCZ region due to the convective mixing deeper boundary layers are formed, where a double structure is observed. The Marine Boundary Layer Height is also estimated using thermodynamic profiles.